Let us know. Btw I have done a bit of tests on my own. Take the bottom glove box off, then remove cover for cabin filter . After that remove the filter. Inside is the recirculate door. I have had my wife drive while I press up on the door and it stops. Anyhow I have scheduled service next Tuesday with a gm engineer. Lemme know what that say.
ps if your in North Carolina , Alabama , Canada reach out to these guys. They work for the dealers and specialize in fixing leaks . The owner that is in Canada states he knows exactly what the problem is and will talk with the tech or advisor : last two dealerships I went to wouldnt speak with him. Don’t know why but ..... they wouldn’t .
https://www.leakpro.com/